Raoul A. Robinson[3] further refined the definition of horizontal resistance.
Unlike vertical resistance and parasitic ability, horizontal resistance and horizontal parasitic ability are entirely independent of each other in genetic terms.
The remaining plants have partial resistance and their seed is stored and bred back up to sufficient volume for further testing.
The hope is that in these remaining plants are multiple types of partial-resistance genes, and by crossbreeding this pool back on itself, multiple partial resistance genes will come together and provide resistance to a larger variety of pathogens.
These plants are exposed to native regional pathogens, and given minimal assistance in fighting them.